<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    姓名：<input type="text" class="username" />
    <button>下一步</button>
    <script>
        let usernaemEle = document.querySelector(".username");
        if(sessionStorage.getItem("username")){
            usernaemEle.value = sessionStorage.getItem("username");
        }

      
        document.querySelector("button").onclick = function(){
            let val = usernaemEle.value;
            sessionStorage.setItem("username",val);
            window.location.href="register2.html";
        }




    </script>
</body>
</html>